Conventional display devices utilize the technique of electron beam to generate light rays and images on a curved or planar range. Limited by the characteristic requirement of electron beam, picture tubes of the conventional display devices are bulky. Therefore, the newest development direction aims to shrink the volume of display device. Display devices integrated with the technique of light-guiding plate start to develop vigorously. For instance, the disclosure of liquid crystal TVs provides a way of saving space in increasingly confined living and working environments of people. The popularization of notebook computers also depends on their greatly reduced weight and compact size. Moreover, improvement in the weight and volume of electronic billboards lets visions and advertisements are more beautiful and diversified. All the above improvements rely on the miniaturization of display panels, wherein light-guiding plates play an important role for effectively changing the usage of light source. Therefore, how to utilize the characteristic of light rays to let everywhere of a light-guiding plate (especially places far away from the light source) have sufficient and uniform brightness is an important direction of improving the light-guiding plate structure.
As shown in FIGS. 1 and 2, a conventional light-guiding plate structure comprises a light source 1a, a light-guiding plate 2a, and a reflective component 3a. The top face of the light-guiding plate 2a is a light output face 20a. The bottom face of the light-guiding plate 2a is a reflective face 21a. A first side 22a, a second side 23a, a third side 24a, and a fourth side 25a adjoining one another in order are disposed at the periphery of the light-guiding plate 2a. The reflective face 21a has veins 26a parallel to the first side 22a. The light source 1a is disposed at the first side 22a. The reflective component 3a covers the second side 23a, the third side 24a, the fourth side 25a, and the reflective face 21a, and also sheathes the light source 1a between it and the light-guiding plate 2a. 
As shown in FIG. 3, the veins 26a of the reflective face 21a of the light-guiding plate 2a are parallel to the first side 22a and the second side 23a. The light source 1a is L-shaped and disposed at the first side 22a and second side 23a. The point of intersection of the first side 22a and the second side 23a is a first end point 27a. The point of intersection of the third side 24a and the fourth side 25a is a third end point 28a. 
Light rays from the light source of the above conventional light-guiding plate structure shown in FIGS. 1 and 2 enter via the first side, are then reflected by the veins of the reflective face, and then project out from the light output face. Because the light source is disposed at the first side, the first side will be too bright while the third side will be darker so that the light rays at the light output face will be nonuniform. Moreover, as shown in FIG. 3, because the light source is disposed at the first side and the second side, the light output face near the first end point will be too bright while the light output face near the third end point will be darker so that the light rays at the light output face will be nonuniform.
Accordingly, the above conventional light-guiding plate structure has inconvenience and drawbacks in practical use. The present invention aims to resolve the problems in the prior art.